For example, in a leadless semiconductor package such as a Small-Outline No Lead (SON) or Quad Flat No Lead (QFN), external connection terminals for connecting to a substrate or the like are exposed on a bottom surface or side surfaces that appear while cutting and dicing a wafer into semiconductor packages. Ordinarily, a plating film is formed before dicing the wafer into the semiconductor packages. Therefore, the plating film is formed on the bottom surface of the external connection terminal exposed on the semiconductor package. However, the plating film is not formed on the side surfaces of the external connection terminals exposed on the semiconductor package.
Therefore, when the semiconductor package is mounted on the substrate or the like using solder, the side surfaces of the external connection terminals scarcely contribute to wet of the solder or connection, but the bottom surfaces of the external connection terminals mainly contribute to the wet of the solder or the connection. As a result, the amount of the solder formed between the semiconductor package and the substrate becomes small. Therefore, stress generated by a difference between thermal expansion coefficient of the semiconductor package and the thermal expansion coefficient of the substrate may cause connection reliability between the semiconductor package to be degraded.
As a measure of improving the connection reliability, a through hole may be formed in the external connection terminal. For example, a solder material or a conductive material such as gold or silver fills the inside of the through hole to prevent a resin from intruding inside the through hole at a time of sealing with the resin. In this example, after dicing into the semiconductor packages, the conductive material filling the inside of the through hole is exposed on the side surfaces of the semiconductor package as a part of the external connection terminals to thereby try to improve the connection reliability as disclosed in the United States Laid-open Patent Publication No. 2011-0108965.